Hydrazine salt for activation and stabilization of chlorite bleach for cellulosic textiles



United States Patent 0 HYDRAZINE SALT FOR ACTIVATION AND STA- BILIZATHON0F CHLORITE BLEACH FOR CEL- LULOSIC TEXTILES Richard L. Doerr, Orange,Conn., assignor to Olin Mathieson Chemical Corporation, a corporation ofVirginia No Drawing. Filed Apr. 14', 1961, Ser. No. 102,966

16 Claims. (Cl. 8108) The present invention relates to improvements inbleaching cellulosic textiles and textile fibers using aqueous solutionsof chlorites.

The present invention is useful in bleaching cotton goods of all kinds,including cotton, linen, jute, hemp and other textile fibers consistingessentially of cellulose as well as cellulose regenerated from a viscosesolution. Also included and successfully bleached by the process of thepresent invention are blended textiles, such as blends of cottons andnylon, cottons and synthetic polyester fibers, cotton andpolyacrylonitrile and other blends containing even minor proportions ofcellulosic fiber. All such textiles are intended to be included in theterm cellulosic textiles and textile fibers as used in the presentspecification and claims.

The bleaching agents normally used in the United States are alkalinehydrogen peroxide, hypochlorite, and chlorites. Chlorite bleachingolfers certain advantages over both alkaline hydrogen peroxide andhypochlorite, especially in that chlorite bleaching is extremelyeffective and economical. Chlorite bleaching shows a substantialimprovement over either hydrogen peroxide or hypochlorite, particularlyin retention of fiber strength, and prov-ides the finisher with a strongfabric as the starting point for chemical finishing operations, forexample, crease-proofing.

When bleaching with acidified chlorite solutions, however, it isnecessary for the fibers to be in contact with the acidified solutioncontaining an adequate amount of chlorite at a pH not above 4. When theaqueous chlorite solution is acidified to a pH of above 4 the bleachingaction is not satisfactory. When the solution is acidified to a pH ofabout 4 or less, however, the solution is unstable on standing and anobjectionable amount of chlorine dioxide gas is evolved. The chlorinedioxide gas is a powerful irritant to the eyes and respiratory systemsof people. Furthermore, it represents a loss of bleaching power sincethe chlorite is being needlessly decomposed.

It is, therefore, an object of the present invention to provide aprocess for bleaching cellulosic textiles and textile fibers withacidified aqueous chlorite solutions.

It is a further object of the present invention to bleach cellulosictextiles and textile fibers in acidified aqueous chlorite solutionsretaining the desirable characteristics of chlorite bleaching whileobtaining improved brightness.

It is a still further object of the present invention to provide anaqueous chlorite bleaching bath which can be acidified to a pH of about4 or less without objectionable chlorite decomposition and evolution ofchlorine dioxide gas.

It is a still further object of the present invention to provide aprocess and aqueous acidic bleaching bath which accomplishes theforegoing objects inexpensively and expeditiously.

Further objects and advantages of the present invention will appearhereinafter.

The foregoing objects and advantages of the present invention may beaccomplished in accordance with the present invention. The novelaqueous, acidic bleaching bath of the present invention has a pH ofbetween 2 and 7 and comprises between about 0.1 and 3.0 percent byweight of a water soluble chlorite and between about 0.001 and 3.0percent by weight of a water soluble hydrazine salt. Cellulosic textilesand textile fibers may be SEARCH ,RDO M 3,111,358 Patented Nov. 19, 1963elfectively, inexpensively and expeditiously bleached by: wetting thetextile to a pickup of 50 to percent with acidified, aqueous chloritesolution having a pH of between 2 and 7 and comprising between about 0.1and 3.0 percent by weight of a water soluble chlorite and between about0.001 and 3.0 percent by weight of a water soluble hydrazine salt;holding the textile at a temperature between about 20 and C. for betweenabout 0.25 and 4 hours; and rinsing the textile in water.

It is surprising to lind that the bleaching bath and process of thepresent invention produces improved bleaching over a bleach effected atthe same pH without the hydrazine salt. This is especially surprisingand unexpected in view of the normally vigorous reaction of concentratedsolutions of hydrazine salts with concentrated solutions of chloritesand in view of the normally explosive reaction of dry hydrazine saltsand dry chlorites. In addition it is surprising and unexpected to findthat when the present invention is employed the bleaching solution maybe kept at a pH of about 4 or below without the usual rapiddecomposition of the chlorite and high incidence of objectionablechlorine dioxide evolution. Since the hydrazine salt inhibits theevolution of chlorine dioxide in the bleaching bath, the corrosion ofstainless steel equipment, a serious problem in the art, is alsomarkedly reduced.

Any water soluble chlorite'tnay be employed. Alkali metal and alkalineearth metal chlorites are normally used, with the alkali metal chloritesbeing preferred. Sodium chlorite is especially preferred because it iscommercially available in the form of Textone, a product of OlinMathieson Chemical Corporation containing about 80 percent sodiumchlorite. Examples of suitable chlorites are lithium chlorite, potassiumchlorite, sodium chlorite, calcium chlorite, barium chlorite andstrontium chlorite.

Any water soluble hydrazine salt may be used in the process of thepresent invention, including partially substituted, water solublehydrazine salts. Partially substituted hydrazine salts are those inwhich the hydrogen attached to the nitrogen of the hydrazine moiety issubstituted by such groups as, tor example, alkyl or aryl groups. Freehydrazine or partially substituted hydrazine may be added to theacidified solution, in which case the free hydrazine or the partiallysubstituted hydrazine reacts with the acid to form the correspondingsalt. The hydrazine salt may be either inorganic or organic. Typicalhydrazine salts include, but are not limited to, the following: mineralacid salts such as, monoor dihydrazine sulfate, monoor dihydrazinephosphate, hydrazine monoor dihydrochloride, hydrazine monoordihydrobromide, hydrazine monoor dihydroiodide, hydrazine borate andhydrazine carbazinate; aliphatic organic acid salts such as, alkanemonobasic carboxylic acid salts, for example, hydrazine formate,hydrazine acetate and hydrazine propionate, alkene monobasic carboxylicacid salts, for example, hydrazine acrylate and hydrazine crotonate,alkyne monobasic carboxylic acid salts, for example, hydrazinepropiolate, saturated dibasic carboxylic acid salts, for example, monoordihydrazine oxalate, monoor dihydrazine malonate, monoor dihydr-azinesuccinate and monoor dihydrazine glutarate, unsaturated dibasiccarboxylic acid salts, for example, monoor dihydrazine maleate andmonoor dihydrazine fumarate, tribasic carboxylic acid salts, forexample, mono-, dior trihydrazine propane-l, 2,3-tricarboxylate andmono-, dior trihydrazine citrate, alkane sulfonic acid salts, forexample, hydrazine methyl sulfonate, hydrazine ethyl sulfona-te andhydrazine propyl sulfonate, halogen or hydroxy substituted salts, forexample, hydrazine mono-, dior trichloro-acetate, hydrazine glycolate,hydrazine lactate, hydrazine Z-hydroxypropionate, hydrazine monoordimalate and hydrazine monoor ditartrate, and amino acid salts, forexample, hydrazine aminoacetate, h rdgagiraJ-aminopropicnate andhydrazine 1-aminoisovalerate; aromatic acid salts such as, hydrazinebenzene sulfonate, hydrazine toluene sulfonate, hydrazine p-halobenzenesulfonate, monoor dihydrazine benzene disulfonate, mono-, dior'trihydrazine benzene trisulfonate, hydrazine phenylsulfonate, hydrazinebenzoate, hydrazine ortho-, metaor para-chlorobenzoate, hydrazineortho-, metaor para-nitrobenzoate, hydrazine salicylate, hydrazinephenylacetate, monoor dihydrazine phthalate, monoor dihyd'razineisophthalate, monoor dihydrazine terephthalate, hydrazine cinnamate,hydrazine o-hydroxycinnamate, hydrazine naphthoate, hydrazinenaphthalene sulfonate and hydrazine naphthenate; cycloalip'hatic saltssuch as, hydrazine hexahydrobenzoate; and partially substitutedhydrazine salts such as, mono-, dior trihydroxyalkyl-substitutedhydrazine salts, mono-, dior trialkylsubstituted hydrazine salts,monoaryl-substituted hydrazine salts and mixed alkyl-aryhsubstitutedhydrazine salts. It is to be understood that mixtures of hydrazine saltsmay be advantageously employed in the process of the present invention.-It is also to be understood that hydrazine salts containing mixedsubstituents may be advantageously employed in the process of thepresent invention.

The concentration of the chlorite in the aqueous solution may be variedfrom between about 0.1 and 3.0 percent by weight, with the concentrationof the chlorite applied to the textile varying from between about 0.1and 3.0 percent by weight based on the weight of the textile. Differenttypes of textiles require different amounts of chlorite to effect amaximum whiteness. Thus a heavy linen may require twice as much as alight cotton. Those skilled in the art of bleaching are familiar withthe requirements of various cellulosic textiles and textile fibers.

The concentration of the hydrazine salt in the aqueous solution may bevaried from between about 0.001 and 3.0 percent by weight, andpreferably between about 0.01 and 0.20 percent by weight. The amount ofhydrazine applied to the textile is appropriately from between about 1and 100 percent by weight of the chlorite, and preferably between aboutand 25 percent by weight of the chlorite.

It is preferred to prepare a single solution containing the requisiteamount of chlorite and hydrazine salt in the proper pH range, immersethe textile in the solution and remove the excess liquid. The textilemay also be wetted by spraying the solution on the textile.Alternatively, two solutions may be prepared, with one solution beingthe aqueous chlorite solution and the other aqueous hydrazine saltsolution. The textile may then be immersed successively in each solutionand excess liquid removed after each immersion.

In the preferred process of the present invention the textile isimmersed in an aqueous solution containing the requisite quantity ofchlorite and hydrazine salt and acidified to a pH of between 2 and 7.The acid used for the acidification is not critical, for example,typical acids include formic, acetic, hydrochloric, sulfuric,phosphoric, or nitric. The textile is then removed from the solution andexcess liquid removed so that the textile has a pickup of from 50 to 120percent based on the weight of the textile. The excess liquid may beremoved by, for example, passing through pre-set squeeze rolls.

After the textile has been wetted with the aqueous solution containingchlorite and hydrazine it is stored until bleaching is complete. Thisprocess is greatly accelerated by heat; a humid atmosphere at about 50to 100 C. for 0.5 to 3 hours is excellent, although a temperature rangeof from 20 to 130 C. for from 0.25 to 4 hours may be employed. Thehumidity can be supplied by applying the heat in the form of steam in asteam box. The humidity may also be supplied by evaporation of a minoramount of the water on the textile if the textile is in a container ofsmall volume which is quickly saturated with water vapor. The solutionon the textile should not lose a material proportion of the water,however, since bleaching is preferably effected by dilgte ch lor itesolutions.

After completion of the holding period the textile is rinsed in waterand dried according to conventional procedures.

The bleaching solution may optionally contain various conventionaladditives which are stable to the components of the bleaching solution.The use of these additives will be apparent to one skilled in the art.Typical additives include the conventional buffers, such as sodiumphosphate and sodium acetate, wetting agents, such as members of theIgepon series (salts of acylalkyl taurides), corrosion inhibitors, suchas water soluble nitrate salts, and chelating agents such as, thoseamines having a plurality of hydrogen groups of the amino group replacedby fatty carboxylic acid groups.

The following examples will further illustrate the present invention andimprovements obtained thereby.

EXAMPLES ll6 In the following examples the textile was immersed in anacidified dilute solution containing cc. of a two percent solution ofsodium chlorite and the indicated amount of a two percent solution ofthe hydrazine salt. The textile was squeezed through pre-set squeezerolls to a pickup of about 85 percent based on the weight of thetextile. The textile was then heated in a steam box at to C. for aboutone hour, rinsed thoroughly in water and dried. None of the textilestreated showed any signs of textile damage. The reflectance was measuredwith a Photovolt Brightness Meter equipped with a tristimulus bluefilter. With the brightness scale used a difference of two units isnoticeable to the unaided eye, while a difference of ten unitsrepresents a striking difference in whiteness. In the brightness rangeabove 80 it becomes increasingly diflicult to obtain each additionalpoint of brightness without damage to the textile; therefore, theimprovements shown in the following examples are of particularcommercial importance.

The following examples utilized a greige cotton textile having aninitial whiteness of 52. When this textile was treated in the abovemanner in a solution acidified to a pH of 3.5 but which did not containa hydrazine salt the brightness was 85.

In the following examples the following abbreviations are used:

MHS=monohydrazine sulfate DHS=dihydrazine sulfate DHP=dihydrazinephosphate Ml-lN monohydrazine nitrate HA=hydrazine acetate Table I 0.0ofa 2% Solution cc. 0fa2% cc. of pH of Example of Hydrazine SaltSolution Water Solution Brightness of Sodium Chlorite EXAMPLES 171 8 Inthe following examples the procedure of Examples ll6 was repeated,except that the textile was heated in a steam box at 94 to 97 C. for 30minutes. There were no signs of textile damage.

Table II cc. ofa 2% cc. of a 2% cc. of pH of Solution of Solution ofWater Solution Example Monohy- Sodium Brightness drazine ChloriteNitrate EXAMPLES l9-25 In the following examples the procedure ofExamples 1-16 was repeated, except that the bleaching solution contained2.5 grams per liter of sodium chlorite and dihydrazine phosphate asindicated and the textile was heated in a steam box for one hour at 210F. There were no signs of textile damage.

T able III Grams per Grams per pH of Solu Liter of Liter of tion ExampleDihydra- Sodium Brightness zine Phos- Chlorite phate EXAMPLES 26-31Aqueous solutions were prepared in a manner after Examples 1-16 and thestability of the solution measured. The stability was measured byobserving the length of time it took for the solution to becomeperceptibly yellow and actively evolve a strong odor of chlorinedioxide.

This invention may be embodied in other forms or carried out in otherways without departing from the spirit or essential characteristicsthereof. The present embodiment is therefore to be considered as in allrespects illustrative and not restrictive, the scope of the inventionbeing indicated by the appended claims, and all changes which comewithin the meaning and range of equivalency are intended to be embracedtherein.

What is claimed is:

1. A process for bleaching cellu losic textiles and textile fibers whichcomprises: wetting the textile to a pickup of 50 to 120 percent withacidified, aqueous chlorite solution having a pH of between 2 and 7 andcomprising between 0.1 and 3.0 percent by weight of a water solublechlorite and between 0.001 and 3.0 percent by Weight of a water solublehydrazine salt; holding the textile at a temperature of between 20 and130 C. for bet-ween 0.25 and 4 hours; and rinsing the textile in water.

2. A process for bleaching cellulosic textiles and textile fibers whichcomprises: wetting the textile with an acidified, aqueous solutionhaving a pH of between 2 and 7 comprising water soluble chlorite toapply to the textile between 0.1 and 3.0 percent of said chlorite byweight of the textile; further wetting said textile with an aqueoussolution comprising water soluble hydrazine salt to apply to the textilebetween 1 and percent of said hydrazine salt by weight of the chlorite;holding the textile at a temperature of between 20 and 130 C. forbetween 0.25 and 4 hours; and rinsing the textile in water.

3. A process for bleaching cellulosic textiles and textile fibers whichcomprises: immersing the textile in an acidified, aqueous solutionhaving a pH of between 2 and 7 and comprising between from 0.1 to 3.0percent by weight of a water soluble chlorite and between 0.001 and 3.0percent by weight of a water soluble hydrazine salt; squeezing thetextile to a pickup of between 50 and percent; holding the textile at atemperature of between 20 and C. for between 0.25 and 4 hours; andrinsing the textile in water.

4. A process according to claim 3 wherein the chlorite is sodiumchlorite.

5. A process according to claim 4 wherein the hydrazine salt ismonohydrazine sulfate.

6. A process according to claim 4 wherein the hydrazine salt isdihydrazine sulfate. 7

7. A process according to claim 4 wherein the hydrazine salt isdihydrazine phosphate.

8. A process according to claim 4 wherein the hydrazine salt ismonohydrazine nitrate.

9. A process according to claim 4 wherein the hydrazine salt ishydrazine acetate.

10. An aqueous, acidic bleaching bath having a pH of between 2 and 7comprising between 0.1 and 0.3 percent by weight of a water solublechlorite and between 0.001 and 3.0 percent by weight of a water solublehydrazine salt.

11. The aqueous, acidic bleaching bath of claim 10 wherein said chloriteis sodium chlorite.

12. The aqueous bleaching bath of claim 11 wherein said hydrazine saltis monohydrazine sulfate.

13. The aqueous bleaching bath of claim said hydrazine salt isdihydrazine sulfate.

14. The aqueous bleaching bath of claim said hydrazine salt isdihydrazine phosphate.

15. The aqueous bleaching bath of claim said hydrazine salt ismonohydrazine nitrate.

16. The aqueous bleaching bath of claim said hydrazine salt is hydrazineacetate.

11 wherein 11 wherein 11 wherein 11 wherein

1. A PROCESS FOR BLEACHING CELLULOSIC TEXTILES AND TEXTILE FIBERS WHICHCOMPRISES: WETTING THE TEXTILE TO A PICKUP OF 50 TO 120 PERCENT WITHACIDIFIED, AQUEOUS CHLORITE SOLUTION HAVING A PH OF BETWEEN 2 AND 7 ANDCOMPRISING BETWEEN 0.1 AND 3.0 PERCENT BY WEIGHT OF A WATER SOLUBLECHLORITE AND BETWEEN 0.001 AND 3.0 PERCENT BY WEIGHT OF A WATER SOLUBLEHYDRAZINE SALT; HOLDING THE TEXTILE AT A TEMPERATURE OF BETWEEN 20 AND130*C. FOR BETWEEN 0.25 AND 4 HOURS; AND RINSING THE TEXTILE IN WATER.